Bleaching cellulose



',@ca 2 E934. F. R. sEAvEY ET AL 1,975,590

` l BLEACHING cELLULosE Filed April 10. 1929 ga/MA' Aggeufs Patented pt. 2, 1934 STATES BLEACHING CELLULO SIE Frederick R. Seavey, Albert J. Phillips, and Fredrich Olsen, Dover, N. J., assignors, by direct and mesne assignments, to The Cellulose Research Uorporation, a corporation of Dela- War@ Application April l0, 1929, Serial No. 354,109

8 Claims.

sion into a transportable form and its subsequentv liberation for use with the attendant unavoidable losses.

The object of this invention is to overcome these objectionable features and to provide a simple, inexpensive process of electrolytically bleaching cellulose, one example, by way of illustration, being the bleaching of wood pulps such as are used in the manufacture of paper and the like.

A further object of the inventionis to provide a new and improved process for bleaching cellulose by the preparation of a mixture of molecular chlorine and oxygen and atomic chlorine and oxygen in intimate contact with the cellulose so as to subject the cellulose to intimate contact with nascent chlorine and nascent oxygen.

In attaining these objects an electrolytic cell is provided having compartments separated by a porous partition adapted to permit diffusion of the electrolyte contained in the cell such as a sodium chloride solution. 'I'he electrodes of suitable material are situated in the compartments, being separated by the porous partition. The cellulose in suspension is placed in the compartment in which the positive electrode or anode is located, the porous partition preventing the cellulose from passing into the compartment containing the negative electrode or cathode. The liberation of chlorine and oxygen at the positive electrode or anode converts the ligneous and other coloring materials into chlorinated derivatives which are slightly soluble in water and may be absorbed by the cellulose. In most instances these derivatives are readily dissolved by washing the cellulose with a hot dilute solution of a sulphite, bi-sulphite, oxalic acid or the like, and a white cellulose remains free of coloring material after a washing in hot water to remove any Y trace of acid.

form of apparatus for carrying out the process of this invention continuously.

Fig. 2 is a plan view showing diagrammatically another form of apparatus for carrying out the process of this invention, and

Fig. 3 is a side elevation of the apparatus shown in Fig. 2.

In the form of apparatus illustrated in Fig. 1 the cellulose suspended in water or other solution is placed in the header box 10 from which it flows through pipe connection 11 to cylinder 12 of bakelite, hard rubber or like insulating material, a portion of which is in the form of a perforated or porous cylinder or a hollow frame work covered by a membrane 13 such as filter cloth or other material which is permeable to ionic flow but which will retain the cellulose within the cylinder.

Within the cylinder 12 is rotated on bearings 14 and 15 a conveyor screw 16 mounted on a shaft 17 for continually agitating and conveying'the pulp through the cylinder 12 to a. discharge pipe connection 18 of insulating material at right angles to the cylinder 12. The pipe connection 18 discharges into a washer 19 from which the cellulose is picked up by the rotating pick up drum 20 such as a continuous rotary lter. The shaft 17 extends beyond the bearing 14 and has a connection 21 with the positive terminal of a supply of electric current so that the conveyor screw 16 and shaft 17 form the anode of the system. The negative side of the circuit is connected at 21 to a cylinder 22 forming the cathode chamber encircling the portion of cylinder 12 which is provided with the membrane 13. The headers 23 of the cylinder are constructed of insulating material. This cathode chamber is adapted for a special bleach liquor if desired such as, for example, sodium sulphite which is pumped therein through pipe connection 24 by pump 25 and the partially reduced residue is permitted to pass out of chamber 22 through pipe connection 26. This cathode chamber, if desired, can be also utilized for bleaching a different form of cellulose than that which is contained in cylinder 12.

When electricity is passed through the apparatus above described the bleaching action takes place with rapidity in the vicinity of the anode, namely the rotating screw conveyor 16.

In the apparatus shown in Figs. 2 and 3 for carrying out the process of this invention the cellulose is bleached in a batch and it is adapted to simultaneously electrolytically bleach two forms of cellulose, if desired.

The tank 27 may be of any desired shape, being illustrated with rounded ends to facilitate' the circulation of the cellulose.-

Within the tank 27 a frame work is provided With a perforated or porous partition or membrane 28 sirniiar to perforated or porous membrane 13 of cylinder lZVdi/'iding the tenis into two chambers, namely a cathode chamber 29 and an anode chamber 30;Y The anodes and cathodes are Vshown in the form of rotating shafts 3l and 32 respectively, provided with a series of agitators 33 which, as the shafts rotate continually, 'agitate the cellulose within the chambers. The shafts are rotated by gearing Sil or any other desired method and are insulated from the'tanl: 27 by insulated bearings 35. The anodes and'cathodes, if desired, may be stationary and any well known agitating means used to agitate the material. desired, one batch of cellulose may be placed in the anode chamber 28 and another batch in the cathode chambeitY 30.

By Way of illustration, one specific example of our invention is as follows: 'l Y A wood pulp slurry havinf7 a consistency of approximately 10% in a 5% sodium chloride solution is placed in a compartment of the cell which is separated by the porous or perforated partition from an external 5% sodium chloride solution. Into the cell is placed a platinum or other suitable electrode and in the external liquid on the other sidelof the membrane another platinum orrother electrode.

ampere per square centimeter of electrode surface at a temperature of 22-25 degrees centigrade for thirty minutes. The main action takes place iii the first fifteen minutes with yellowing of the pulp and a diminution in the amount of lows till no trace of acidity in the wash water remains. W l

While this invention has been illustrated and described more particularly with reference to'a process of bleaching cellulosesuch as the Wood pulps usually used in the manufacture of paper and the like, the invention is not confined thereto but is intended to cover any other useslor modifications within the scope of the appended claims. Y

We claim :n ,Y

1. 'I'he process of treating cellulose comprising forming a slurry thereof in an aqueous solution of a salt, continually moving said slurry in constant contact with a movable anode terminal of an electric circuit while current is flowing through said slurry to complete said circuit, retaining said slurry from Contact with the cathode terminal and continuing the exposure of the cellulose to the electrolytic action of said current substantially uniformly so as simultaneously to treat all portions of the cellulose the same.

2. The process of bleaching cellulose comprising forming a slurry thereof in an aqueous solution of a chlorine salt, the slurry having a consistency of approximately ten percent in a live percent solution, continually moving said slurry in constant contact with a movable anode terxninal of an electric circuit while current is flowing through said slurry to complete said circuit, retaining said slurry from contact with the cathode terminal, and continuing the exposure of the cellulose to the electrolytic action of said current for not over one hour so as to subject all portions of the cellulose simultaneously to substantially the same treatment with nascent chl0= rine.

The solution is elec-l trolyzed with aYY direct current of about one incasso E. in apparatus for bleaching cellulose the combination with a central container and a surrounding conteiner, a porous partition nmans between said containers, of a source of electric current having its positive terminal in one container andwits negative terminal in the other so that current 'will pass through solutions in said containers to treat pulp slurry therein and means for agitating said slurry in each. of said containers.

rfi. ln .apparatus for bleaching cellulose the combination with a central container and a surrounding container each adapted for treatment of a slurry of cellulosic material, a porous partition means between said containers, or" a source of electric current having Yits positive terminal in one container and its negative terminal ,in the other so that current will pass through solutions in said containers to treat pulp in each of said containers.

l 5. ln apparatus for bleaching cellulose the combination with a central container and a surrounding container, a porous partition means between said containers, of a cource of electric current having its positive terminalin one container and its negative terminal in the other so that current will pass through solutions in said containersto treat pulp in at least one thereof, and means for moving one of said terminals to feed the pulp through the corresponding container.

6. A process of bleaching pulp comprising forming the pulp in a slurry of an aqueous solution of a chlorine salt, providing a-container having an anode chamber with an exposed anode adapted to bein movable contact with said slurry, moving said slurry continuously through said chamber in constantly shifting contact with said anode, positioning the cathode in a chamber opposite to the anodeY so that the current ows through the slurry and subjects all portions of it simultaneously to substantially the same bleaching action, separating the slurry from the cathode by a porous partition and supplying current to effect the desiredbleaching action during the continuous movement of the slurry alonglzthe anode surfaces. Y

'7. In apparatus for bleaching cellulose the combination with a container having means t0 move a, cellulose slurry fromend to end thereof, an anode within said container in Contact with said moving slurry, a cathode spaced outwardly from said anode, porous partition means between said anode and cathode retaining said slurry from contact with said cathode, and means for iiowing an electric current between saidanode and cathode so that said current is distributed throughout the entire mass of the passing slurry.

8. The process of bleaching cellulose comprising forming a slurry thereof in an aqueous solution of a chlorine salt, continually moving said slurry in contact with an anode terminal of an electric circuit while current is flowing through said slurry to complete said circuit, cont'muously retaining said slurry from contact with the cathode terminal, continuing the exposure of the cellulose substantially uniformly to the electrolytic action of said current adjacent said anode and spaced from said cathode, separating the cellulose from the liquid, then dissolving out chlorinated lignins and finally washing said cellulose with water until .no trace of acidity in the wash water remains.

FREDERICKR. SEAVEY. ALBERT J. PHILLIPS. FRIEDRICH CLSEN. 

